Forages are rapid biomass-generating crops that often demand intensive management. They necessitate a clear understanding of energy flow and carbon (C) footprinting which in turn helps in optimization of production resources and environmental impact assessment. Therefore, a field experiment was conducted for five consecutive years (2019–2023) to ascertain eight forage crops’ productivity, energetics, and C footprint. The crops under the annual monoculture system were maize and cowpea. While, Napier, Guinea, Rhodes, Green panic, Anjan grass, and Signal grasses were under perennial monoculture system. The results revealed that, the Napier grass was superior in biological productivity by recording 28%–50% higher green fodder yield over other forages. The energy analysis indicated that the Guinea grass consumed the highest energy (61,719 MJ ha−1 Year−1) during production, while Napier grass showed the highest energy output (32,5991 MJ ha−1 Year−1). Further, Napier grass outperformed the rest in terms of energy use efficiency (5.49), energy productivity (2.39 kg MJ−1), net energy gain (266,641 MJ ha−1 Year−1), energy profitability (4.49), nutrient energy ratio (14.7), and human energy profitability (558). Similar to energy input, Guinea grass production showed the highest C input (970 kg-CE ha−1 Year−1). Whereas, highest C output was observed with Napier grass (56,694 kg-CE ha−1 Year−1) due to its substantial C gain (55,805 kg-CE ha−1), C-efficiency ratio (63.79), and C-stability index (0.98). Consequently, Napier grass can be adopted as a productive, energy profitable, and C-efficient forage crop in semi-arid tropical conditions.